U.S. patent number 5,808,417 [Application Number 08/650,076] was granted by the patent office on 1998-09-15 for lighting control system with corrugated heat sink.
This patent grant is currently assigned to Lutron Electronics Co., Inc.. Invention is credited to Jonathan H. Ference, Donald F. Hausman, John F. Loar, Robert S. Spehalski, Walter S. Zaharchuk.
United States Patent |
5,808,417 |
Ference , et al. |
September 15, 1998 |
Lighting control system with corrugated heat sink
Abstract
A dimmer panel for controlling the intensity of a plurality of
electric light sources includes a plurality of dimming circuits.
Each dimming circuit has a control circuit, a heat producing
controllably conductive power switch such as a triac, and a heat
producing coil such as a choke. The power switches and coils are
arranged on a corrugated heat sink to minimize component
temperatures in the dimming control circuit and of the power
switches. The heat producing coils are remotely located from the
control circuit and the power switches, so that the heat generated
by the coils does not increase the temperature of the components in
the control circuit or of the power switches.
Inventors: |
Ference; Jonathan H.
(Riegelsville, PA), Hausman; Donald F. (Emmaus, PA),
Loar; John F. (Allentown, PA), Spehalski; Robert S.
(Emmaus, PA), Zaharchuk; Walter S. (Allentown, PA) |
Assignee: |
Lutron Electronics Co., Inc.
(Coopersburg, PA)
|
Family
ID: |
22847955 |
Appl.
No.: |
08/650,076 |
Filed: |
May 17, 1996 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
226194 |
Apr 11, 1994 |
5530322 |
|
|
|
Current U.S.
Class: |
315/112; 315/195;
315/DIG.4 |
Current CPC
Class: |
H05B
47/18 (20200101); H05B 47/155 (20200101); H05B
39/086 (20130101); H05B 39/08 (20130101); H05B
47/165 (20200101); Y10S 315/04 (20130101) |
Current International
Class: |
H05B
39/08 (20060101); H05B 39/00 (20060101); H05B
37/02 (20060101); H01J 007/24 () |
Field of
Search: |
;361/674 ;174/DIG.2
;315/291,195,DIG.4,112,117,118 ;336/59,65,66,90,96 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pascal; Robert J.
Assistant Examiner: Vu; David H.
Attorney, Agent or Firm: Seidel, Gonda, Lavorgna &
Monaca, PC
Parent Case Text
This is a divisional of application Ser. No. 08/226,194 filed on
Apr. 11, 1994 now U.S. Pat. No. 5,530,322.
Claims
What is claimed is:
1. A dimming panel for controlling the intensity of a plurality of
electrical light sources, said dimming panel comprising a thermally
conductive support plate having a plurality of heat-generating
dimming circuits disposed thereon, said support plate being a
continuous serpentine sheet of material having a selected
substantially uniform thickness and being shaped to form a
plurality of first flats and second flats, said first flats and
said second flats being substantially parallel to one another and
being joined by portions of said continuous sheet which define wall
portions disposed at an angle to said first and second flats, said
first and second flats and said wall portions defining open
channels between opposing wall portions.
2. The apparatus as defined by claim 1 wherein each of said dimming
circuits comprises a controllably conductive device and a
heat-producing coil, said dimming circuits disposed so that their
respective heat-producing coils are disposed on said support plate
at a location remote from their respective controllably conductive
devices.
3. The apparatus as defined by claim 2 wherein said dimming
circuits are disposed on said support plate in a pattern such that
more of said controllably conductive devices are disposed at the
support plate's periphery than at the central region thereof.
4. The apparatus as described by claim 2 wherein said dimming
circuits are disposed on said support plate so that all of their
respective controllably conductive devices are thermally coupled to
only said first flats or second flats of said support plate and
said coils are thermally coupled to both the first and second flats
of said support plate.
5. The apparatus as defined by claim 1 wherein said support plate
is made of aluminium and has a thickness of about 3 mm.
6. The apparatus as defined by claim 1, wherein said first flats
are coplanar and define a common first plane and said second flats
are coplanar and define a common second plane, said first and
second planes being parallel and spaced apart by a preselected
distance, said wall portions connecting said first and second
coplanar flats and defining a first plurality of channels having
open ends coplanar with said first planes and a second plurality of
channels having open ends coplanar with said second planes.
7. The apparatus as defined by claim 6 wherein the depths of said
channels is about 25 mm.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvements in relatively
sophisticated lighting control systems of the type used most often
in commercial settings for controlling the luminous output of a
large number of lighting fixtures which are grouped together in
some manner to define various "zones" of light.
2. Description of Related Prior Art
In many commercial lighting applications where large numbers of
lighting fixtures (say, for example, several hundred) are used to
illuminate areas of interest, it is common to group the fixtures in
such a manner as to define "zones" of light which can be
independently controlled from one or more wall-mounted control
units. The wall-mounted control units are typically located in the
vicinity of the lights they control. Each control unit usually
comprises an array of manually manipulatable zone-intensity or
"dimming" actuators, such as sliders or up/down push-buttons, each
actuator being specifically assigned or dedicated to a particular
lighting zone. Manipulation of any one of these actuators serves to
vary a characteristic of a lighting control signal transmitted by
the control unit and used to control the output of one (or more)
dimming circuits or modules, hereinafter referred to as "dimmers,"
which apply power to each of the lighting fixtures defining a
particular lighting zone. In addition to providing a means for
adjusting the instantaneous light level of several zones of light,
each control unit is usually adapted to store preset values for
each of the lighting zones controlled by its respective actuators.
In response to the actuation of any one of several "scene-select"
switches on the control unit, stored preset values can be
simultaneously recalled for all of the lighting zones, thereby
creating any one of several different lighting scenes in the area
illuminated by the preset lighting zones. Such multi-zone,
multi-scene lighting control units are commercially available, for
example, from Lutron Electronics Co. Inc. under the registered
trademark "Grafik Eye".
As noted above, it is common to locate the lighting control units
in the vicinity of the lighting fixtures they control. The dimmers
through which they control power to the fixtures, however, are
usually mounted in a centrally located power cabinet which is
remote from the control units and lighting fixtures. Communication
between the control units and the power cabinet has been achieved
by a digital communications link in which the control units
sequentially transmit, in a multiplex fashion, zone-intensity
information on a low voltage communications bus. The multiplexed
information is decoded in the power cabinet by a microprocessor
forming part of a dimmer control panel circuit which controls the
operation of the dimmers. Upon decoding the multiplexed
zone-intensity information and determining, for example, through an
appropriately programmed look-up table, which of the dimmers is to
receive and act on certain zone-intensity information received by
the microprocessor, the dimmer control panel circuit transmits such
information to the appropriate dimmers. While it is known to
transmit this data to the dimmers on wires connecting each dimmer
to the dimmer control panel circuit, it is also known to multiplex
such transmission on a digital communications link. In the latter
case, each dimmer is assigned a unique binary (or digital) address
code, and it responds only to zone-intensity information on the
link that is preceded by (or somehow associated with) its
respective address code. A microprocessor associated with each
dimmer processes the address and zone-intensity information and
outputs a dimming control signal which is used to control the
firing angle of a triac or the like, thereby adjusting the RMS
voltage applied to the associated lighting load and, hence, its
luminous output.
In the past, "digital" dimmers of the above type have employed
either an array of bi-stable "DIP" switches or one or more
multipositional rotary selector switches to define the unique
address code of each circuit. See, for example, the digital dimmers
made by Lite-Touch Inc. In the case of the bi-stable DIP switches,
for example, the binary address code of each dimmer is set during
system installation by moving a small switch actuator on each
switch of the array to one of its two stable positions. It will be
appreciated that, in the event that one or more of the dimmers
needs replacement, the system user is required to manually set the
state (or position) of the address switches of the replacement
dimmer to assure that the replacement dimmer responds only to the
zone-intensity information intended for the dimmer that has been
replaced. Should this detail be overlooked or not understood, a
service call may be required to correct the situation.
In addition to the digital addressing problem noted above,
multizone lighting systems of the above type are notoriously
difficult to modify (e.g., add dimmers or change the assignment of
zone-intensity actuators) once the system is installed and
operating. It will be appreciated that, during set-up and
check-out, written documentation is always available to correlate
each dimmer with the zone-intensity actuator that controls its
output. Such documentation is usually in the form of a listing that
assigns each dimmer to a particular zone actuator. This listing is
desirable when it comes time to program the dimmer control panel
circuit's look-up table that correlates the individual
zone-intensity actuators with the dimmers. Should this
documentation be unavailable or not readily understood at the time
when modifications or additions to the system are required, a great
deal of time can be expended in determining what actuator controls
what circuit, and what symbology was used to identify the zone
actuators so that re-programming of the look-up table can be
carried out. Say, for example, a lighting system comprises three
wallbox control units, U1, U2 and U3, disposed at different
locations within a lighting region, and each control unit is
capable of controlling six lighting zones through the manipulation
of six zone-intensity actuators A1 through A6. Further assume that
the system comprises 24 dimmers which control power to the various
lighting fixtures of the system. In programming the dimmer control
panel circuit's look-up table, it is necessary to assign each
zone-intensity actuator to one or more dimmers. To conserve memory
space, this programming is effected by using some abbreviated
symbology, such as "U2, A3" and "D19" to identify a particular
zone-intensity actuator and its assigned dimmer circuit,
respectively. Should one desire to add a new dimmer to the system,
one must not only possess the apparatus required to effect
re-programming, but also one must have the knowledge of the
symbology used in programming the power panel. Even having this
information, the system user would then have to know how to program
the power panel, a daunting task for all but a few. Ideally, the
user should be able to add a new dimmer without need for
consultation and/or assistance from the system installer.
A further problem associated with multi-zone lighting control
systems of the above type is that of providing an efficient and
low-cost means for dissipating the substantial levels of thermal
energy generated by each of the dimming circuits so that a large
number of such circuits (e.g., 24) can be housed in a relatively
compact space. As noted above, each dimming circuit includes a
power switching device, e.g., a triac, which serves to interrupt
the line voltage applied to a lighting load for a preselected
period during each half-cycle to control the RMS voltage across the
load. It also includes a relatively large choke or coil which forms
part of a radio frequency interference (RFI) suppression and lamp
de-buzzing network. When the dimmer is operating, both of these
components heat to temperatures well in excess of 100 degrees
Centigrade and act to irradiate the other components of the dimmer
module. To assure proper performance of the dimmer, it is common to
thermally couple the power-switching device and RFI choke to a
relatively elaborate heat sink, e.g. an aluminum plate with
heat-dissipating fins. Further, it is common practice to either
select the other dimmer circuit elements for their ability to
withstand and operate under high temperature conditions, or to
provide sufficient spacing between the heat-generating components
and other components. As may be appreciated, these
temperature-compensating measures tend to add significant cost to
the lighting control system, and/or enlarge the physical size of
the dimming panel, i.e., the structure that supports multiple
dimming circuits.
Additional drawbacks of existing digital dimmers of the above type
are: 1) the dimming circuits are not easily by-passed to provide
emergency or temporary lighting in the event of a loss of the
dimming control signal; in such event, jumper cables are usually
used to by-pass or shunt the dimmer and thereby connect the
lighting load directly to the line voltage; 2) their voltage
compensation circuitry is tailored for different nominal line
voltages (e.g., 110 or 277 volts), thereby requiring different
dimmer circuits for different localities; and 3) they can be
difficult to trouble-shoot in the event of system or component
failure.
SUMMARY OF THE INVENTION
In view of the foregoing discussion, one object of this invention
is to provide a multizone lighting control system of the above type
in which there is no need for written documentation in assigning a
zone-intensity actuator to a selected dimmer.
Another object of this invention is to provide a digital dimmer
that requires no conscious operator involvement in setting its
unique binary address code.
Another object of this invention is to provide an improved dimming
circuit panel which, owing to the arrangement of the
heat-generating components of a pluraliity of dimming circuits on a
specially contoured metal support plate, is especially efficient in
dissipating heat, thereby allowing the use of components with
relatively low temperature ratings, and/or allowing more dimming
circuits to be housed in given area.
Another object of this invention is to provide a simple means for
providing temporary lighting at a preset level in the event of a
loss or absence of a dimming control signal normally used to
control the output of a dimmer to a lighting load.
Still another object of this invention is to provide a voltage
compensation circuit for stabilizing the lighting system
performance notwithstanding voltage variations of a transient
nature, such circuit being independent of the nominal line
voltage.
A further object of this invention is to provide a low-cost
apparatus for detecting control unit or dimmer failure in lighting
systems of the above type and for providing a visual indication of
such failure to the system user.
According to one aspect of the invention there is provided an
improved multi-zone lighting control system for selectively
controlling the respective light levels of a plurality of lighting
zones, each of such zones comprising a dimmable light source.
According to a preferred embodiment, such lighting control system
comprises:
(a) a lighting control unit for multiplexing zone-intensity
information on a communications link, such zone-intensity
information representing desired light levels for each of the
plurality of lighting zones, such lighting control unit including a
plurality of manipulatable dimming actuators, each being adapted to
adjust the zone-intensity information to reflect a desired change
in light level for a different one of the lighting zones; and
(b) dimming control means operatively connected to the lighting
control unit and responsive to the multiplexed zone-intensity
information on the communications link for adjusting the light
level of the dimmable light sources to achieve the desired light
level in each of the lighting zones. Preferably, the dimming
control means includes:
(i) a plurality of dimmers, each being adapted to control the
luminous output of a light source in one of the lighting zones in
response to receiving a dimming control signal; and
(ii) means for assigning each of the dimmers to a particular
dimming actuator so that the respective input signal received by an
assigned dimmer is determined by the zone-intensity information
adjusted by such particular dimming actuator, such assigning means
comprising: (1) means for selecting a particular dimmer, and (2)
means responsive to a predetermined sequence of changes of
zone-intensity information on the communications link as produced
by a predetermined manipulation of any one of the dimming actuators
to assign such one dimming actuator to the selected dimmer.
According to a second aspect of this invention, there is provided a
self-addressing dimmer that is adapted for use in a digital
lighting control system of the type comprising a central control
unit which communicates with a plurality of such dimmers over a
common communications link to control the power applied to a
plurality of lighting loads. Each of the dimmers comprises (i) a
housing (e.g. a circuit board) adapted to be mounted in a
predetermined location on a support plate, and (ii) means for
storing a unique binary address code by which the central control
unit can communicate exclusively with any one of the dimmers over
the common communications link. Preferably, the address
code-storing means comprises a plurality of electrical switches
mounted on the associated housing of each dimmer, each of such
switches having means for controlling the conductive state (open or
closed) of its associated contacts. According to this aspect of the
invention, the state-controlling means of each switch is
controllable by switch-controlling means disposed on the support
plate. Thus, as the dimmer is mounted on the support plate in its
proper position, the switch-controlling means on the support plate
cooperates with the state-controlling means on the dimmer housing
to selectively and automatically set the respective conductive
states of the switches, thereby setting the address of the dimmer.
Preferably, the state-controlling means of each switch is in the
form of a push button or plunger-type switch actuator which is
spring-biased toward an outwardly extending position, and the
switch-controlling means on the support plate comprises an array of
holes and lands in the support plate. When a dimmer is properly
mounted on the support plate, the lands interact with selected
switch actuators, causing them to move from their respective biased
positions to their non-biased positions. Meanwhile, the holes allow
the remaining switch actuators to remain in their respective biased
positions. When a single support plate is used to support multiple
dimmers, the support plate is provided with multiple unique hole
and land patterns opposite each location that is intended to
support a dimmer. Thus, the address of each dimmer is determined by
its position on the support plate.
According to a third aspect of this invention, there is provided an
improved dimming panel which includes a thermally conductive
support plate and a plurality of dimming circuits each having a
heat-producing power switching device and a choke. According to a
preferred embodiment, the support plate has a corrugated
cross-section, and the respective chokes of the dimming circuits
are mounted in close proximity to each other on the support plate
at a location remote from their associated dimming circuits. This
has the effect of substantially lowering the ambient temperature in
the vicinity of the other circuit components, thereby prolonging
their respective lifetimes.
According to a fourth aspect of this invention, there is provided a
temporary lighting feature by which a preset lighting level can be
provided in the event there is a loss or absence of the control
signal used to control the output of the digital light dimmers.
According to this aspect of the invention, means are provided for
(a) sensing the absence of the control signal; (b) switching power
OFF and ON to the dimmer: and (c) detecting the occurrence of both
(a) and (b) and, in response thereto, applying a predetermined
dimming level control signal to a control circuit adapted to
control, e.g., through a triac, the current flow through a lighting
load to selectively adjust the luminous output thereof.
According to a fifth aspect of this invention, there is provided an
improved voltage compensation apparatus which is adapted for use in
a light dimmer for maintaining a substantially constant load
current notwithstanding short-lived changes in the line voltage.
The apparatus is useful with any conventional A.C. line voltage
source (e.g. 100, 120, 220 or 277 volts, 50 or 60 hertz) and
preferably comprises:
(a) means operatively connected to the A.C. voltage source for
determining a first time interval representing the average time
required for the A.C. waveform to reach a predetermined threshold
level during each half cycle of a nominal operating period;
(b) means operatively connected to the A.C. power source for
determining during each half cycle of the waveform a second time
interval representing the time required for the A.C. waveform to
reach such predetermined threshold level;
(c) means for comparing the first and second time intervals during
each cycle of the waveform and for producing an error signal
representing the difference in such time intervals; and
(d) means for adjusting the firing angle of a triac or the like
used to control the power applied to the lighting load according to
the value of the error signal to maintain the RMS voltage across
the lighting load at a substantially constant level notwithstanding
short-lived variations in the amplitude of the A.C. waveform of the
voltage source.
According to a sixth aspect of this invention, there is provided a
diagnostic apparatus adapted for use in a light dimmer of the type
which selectively controls the current flow through a lighting load
to adjust the luminous output thereof, such light dimmer comprising
(i) a controllably conductive device (e.g. a triac) connectable in
series between an A.C. power source and a lighting load, and (ii) a
control circuit which responds to a dimming level control signal
provided by a lighting control unit to selectively apply a selected
portion of an A.C. voltage waveform produced by the A.C. power
source to the lighting load to adjust the RMS voltage across the
lighting load, such selected portion being determined by a phase
angle at which the control circuit causes the controllably
conductive device to conduct power during each half cycle of the
A.C. waveform. According to this aspect of the invention, the
diagnostic apparatus comprises:
(a) means for sensing the operating status of a component of the
dimmer and/or the presence of the dimming level control signal;
(b) logic and control means for comparing an output of the sensing
means indicating the present operating status of the component
and/or the presence of the dimming level control signal with a
stored value; and
(c) a status indicator, preferably a single light-emitting diode,
which responds to an output of the logic and control means to
provide a visual indication of a change in status of the component
and/or the presence of the control signal.
The invention and its various aspects will be better understood
from the ensuing detailed description of preferred embodiments,
reference being made to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a multi-zone lighting control system
of the type in which the inventions disclosed herein are
useful;
FIG. 2 is a more detailed block diagram of the dimmer control panel
of the FIG. 1 system;
FIG. 3 is a front plan view of an interactive display panel useful
in programming the programmable dimmer control panel of the FIG. 1
system;
FIGS. 4A and 4B are flow charts of a computer program adapted for
use in the FIG. 1 system for assigning a desired zone-intensity
actuator to a selected dimmer;
FIG. 5 is a block diagram of a digital dimmer embodying various
aspects of the invention;
FIG. 6 is a perspective view of a portion of a support plate
adapted to support a plurality of the dimmers;
FIG. 7 is a perspective view of a dimming panel illustrating a
preferred layout of dimming circuits and chokes;
FIG. 8 is an end view of a portion of the dimmer panel shown in
FIG. 7;
FIGS. 9A-9B, 10A-10C, and 11A-11B are flow charts illustrating
various programs carried out by the microprocessor component of the
dimmer shown in FIG. 5; and
FIGS. 12A-12D is an electrical schematic showing preferred
circuitry for implementing various aspects of this invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, FIG. 1 schematically illustrates a
multi-zone lighting control system in which a plurality of lighting
control units U1, U2, U3 operate through a plurality of dimmers
(dimmer 1 through dimmer N) to control the output intensity of a
plurality of lighting loads L1 through LN. While each of the
lighting loads is schematically depicted as comprising a single
fixture, it will be appreciated that each lighting load usually
comprises several, and often many, individual lamps of the same
type, e.g., all being either incandescent, fluorescent, neon, etc.
As shown, the lighting loads may be grouped together to define a
plurality of lighting zones Z1, Z2, Z3, . . . ZN, the light
intensity of each zone being controlled by the output of one or
more of the dimmers. In the FIG. 1 system, control units U1-U3 are
of conventional design, each comprising a plurality of
zone-intensity actuators A1-A6, shown as sliders, which can be
manually manipulated, such as raised or lowered within slots S1-S6,
respectively, to vary a characteristic of a lighting control signal
produced at the output x of each unit. As explained below, the
respective outputs of the control units serve to control the
respective outputs Y of the dimming modules and, hence, the light
intensity of the lighting zones. Each of the actuators A1-A6
controls one or more dimmers to control the light intensity in a
particular lighting zone to which the dimmers are assigned, e.g.
actuator A1 of control unit U1 may control the lighting intensity
in zone Z1 by controlling the outputs of dimmers 1 and 2; actuator
A1 of control unit U2 may be assigned to control the output of
dimmer 3 which controls the lighting intensity in zone Z2; and
actuator A4 of control unit U3 may be assigned to dimmers 4 and 5
which control the lighting intensity in zone Z3. In the control
units shown, physically moving the slide actuator in the slot acts
to raise or lower the light level. In some control units, however,
the zone-intensity actuator may take the form of a pair of UP/DOWN
push buttons which, through suitable circuitry, have the same
effect on the control unit output. Suitable control units for the
FIG. 1 system are the so-called Grafik Eye Lighting Controls,
Models 3000 or 4000, made by Lutron Electronics Co., Inc.
Lighting control units U1-U3 are usually wall-mounted devices, each
being mounted in a wallbox located in the vicinity of the lighting
fixtures they control. The control units communicate with the
various dimming modules through a programmable dimmer control panel
circuit CP which, together with the dimming modules, is housed in a
power cabinet PC located remote from the controls and lighting
fixtures, e.g. in a power control room. The dimmer control panel
circuit includes a microprocessor 20, such as a Motorola Model
68HC11E9, eight-bit microcontroller, which receives multiplexed
zone-intensity information transmitted by the control units over a
digital communications link MUX. Upon being sequentially polled in
a conventional manner, each control unit transmits, in accordance
with an established protocol, a serial message on the link, such
message representing digitally encoded zone-intensity information
determined by the position of its six zone actuators. Polling of
the control units is typically effected at a relatively fast rate,
e.g., once every 100 ms., each control unit taking its turn in a
predefined time-slot. Upon receiving and de-multiplexing the zone
intensity information from the lighting control units, the
microprocessor stores this information in a conventional random
access memory (RAM) 22, updating the memory with fresh intensity
information during every poling cycle. As shown in FIG. 2 which
illustrates certain preferred details of the dimming control pane
circuit, the zone-intensity information is stored in tabular form,
each box (e.g., U1, A1, which identifies actuator A1 of control
unit U1) containing eight bits of zone-intensity information for
the associated zone actuator for the preceding polling cycle. In
the system depicted in FIG. 1, there are a total of eighteen zone
actuators; hence, RAM 22 must accommodate eighteen intensity
levels, one for each actuator.
Still referring to FIGS. 1 and 2, the dimming control panel circuit
further comprises a look-up table (LUT) 24, preferably a standard
electrically erasable read-only memory (EEPROM); a programmable
read-only memory (PROM) 26 (described in considerable detail
below); and a programming unit 28 including an interactive display
30 through which the look-up table can be programmed to assign each
dimming module to a particular zone actuator. While shown
separately, it will be appreciated that the look-up table and PROM
are often integral portions of the microprocessor and, in fact, are
part of the Motorola microcontroller mentioned above. In the
example shown in FIG. 1, it is shown that dimmers 1 and 2 control
the lamps in lighting zone Z1. Therefore, in setting up the
lighting system, it is necessary to assign dimmers 1 and 2 to a
single zone actuator, and to store that assignment in the look-up
table. As shown in FIG. 2, dimmers 1 and 2 have been assigned to
zone actuator U1, A1, i.e. actuator A1 of control unit U1. This
assignment is normally achieved by appropriately programming LUT 24
through the programming unit 28. Similarly, FIG. 1 shows that
dimming module 3 controls the lamps of zone Z2. In FIG. 2, it is
shown that the look-up table has been programmed to assign actuator
U1, A2 to this particular lighting zone. Further, it is shown in
FIG. 1 that dimmers 4 and 5 control the lamps in zone Z3. Referring
to FIG. 2, control of these dimmers has been assigned in the
look-up table to zone actuator U1, A3.
Referring to FIG. 3, the programming unit 28 includes an
interactive display 30 which is illustrated as comprising a pair of
seven-segment LED (light-emitting diodes) displays 32, 34; a series
of push-button switches 35-39; and an array of single LEDS 40-45.
Display 32 is part of the "Select Circuit" portion of the
programmer display and is adapted to show a number representing a
particular dimming circuit number. A desired dimming circuit number
is selected by repeatedly depressing the appropriate UP/DOWN
buttons 35, 36 until the display 32 shows the desired circuit
number. Assignment of the selected circuit to a particular zone
actuator is achieved in the "Select Value" portion of display
30.
Upon selecting the desired dimmer and entering a program mode
(e.g., by depressing buttons 35 and 39 simultaneously for a
predetermined time period), button 39 is repeatedly depressed,
thereby causing the LED's 40-45 to become illuminated, one at a
time. These LED's respectively identify various internal programs
that are stored in PROM 26, each program enabling the user to
adjust certain dimmer parameters and store certain values. When LED
40 is illuminated, for example, a program is accessed which allows
the user to chose one of four different load types (i.e.
incandescent or low voltage, fluorescent, neon or cold cathode, or
non-dimmable) by depressing the UP/DOWN buttons 37, 38 until the
number (from 01 to 04) is shown on display 34. Based on the load
type chosen, the programming unit causes the microprocessor 20 to
transmit a load-type signal to the selected dimming module, causing
the dimming module to chose an appropriate calibration curve
(stored in memory of the dimming module) for dimming the lamps
controlled thereby. When LED's 43 or 44 are illuminated, programs
are accessed which allow the user to set either the lowest or
highest intensity level available for the selected dimmer. When LED
41 is illuminated, the operator can assign a desired zone actuator
to the selected dimmer through the interactive display. At this
time, the seven-segment display 34 alternately displays, for one
second intervals, a particular control unit number, e.g. U1, and a
particular actuator number, e.g., A1. By depressing the UP/DOWN
buttons 37, 38 at the appropriate time, the operator can increment
the displayed number by one and thereby select a desired control
unit and zone actuator. Having selected both the dimming circuit
number and actuator number, the microprocessor assigns (or
re-assigns) this particular actuator to the selected dimming
circuit after a preset time interval has elapsed, and stores this
assignment in the look-up table LUT 24.
As may be appreciated, assigning a particular zone actuator to a
dimmer in the manner described above requires knowledge by the
programmer of the actuator symbology. At initial set-up of the
system, there is always some documentation, e.g., a work sheet,
that correlates these two variables, control unit number and
actuator number, in a symbology understood by the microprocessor.
With the passage of time, however, such documentation often
disappears, and even the smallest change in actuator assignments,
or the addition of a new circuit to the system, often requires a
service call to the system installer who presumably has retained
the necessary documentation to make a change.
According to a one aspect of this invention, the above-noted
difficulty in making modifications to an existing lighting system
of the type described is alleviated by the provision of a computer
program that obviates the need for any documentation in order to
re-program the look-up table 24 with new zone actuator assignments.
According to a preferred embodiment, this program, which is stored
in PROM 26, causes the apparatus to carry out the sequence of steps
shown in the flow chart of FIG. 4. Upon entering a programming mode
as described above, pushbutton 39 is repeatedly depressed until LED
42 is illuminated. This LED indicates that the "Zone Capture"
program has been accessed. The operator then selects a dimming
circuit for zone actuator assignment by depressing UP/DOWN buttons
35, 36. Having made the circuit selection, the microprocessor
outputs a signal to the selected dimmer, causing the lamps on the
selected circuit to repeatedly flash, full ON and OFF. This
flashing is intended to give the operator a visual indication of
the lights controlled by the selected dimming circuit. The operator
then goes to the specific actuator which is intended to be assigned
to the selected dimming circuit and physically moves or manipulates
the actuator so as to request a minimum light level. In the control
shown in FIG. 1, the operator would move the slider to the bottom
of its respective slot. Upon detecting that any of values stored in
RAM 22 are at the minimum allowed level, the microprocessor sets a
binary bit or flag. Having manipulated an actuator to request
minimum light level, the operator is then required to manipulate
the actuator towards a position requesting maximum light intensity,
e.g. moving the slider towards the top of the slot. At this time,
the microprocessor starts an internal timer which sets a time
period (e.g. 5 seconds) during which the next sequence of events
must be completed in order to assign the manipulated actuator to
the selected dimming circuit. The operator then continues adjusting
the slider towards a position requesting maximum light level.
During this time, the microprocessor monitors the intensity values
of the zones for which a flag was set at the beginning of the
timing period. As soon as one of the zones, presumably the zone
whose actuator is being adjusted, reaches a predetermined value,
say, 50% of maximum value, the microprocessor causes the light
intensity of the lamps on the selected dimmer circuit to stop
flashing and track (in intensity) the adjustment or movement of the
actuator. At this point, the selected dimmer has now been
"captured" by the actuator. Upon noticing that the lamp(s) on the
captured dimmer are tracking the actuator adjustment, the operator
begins to adjust the zone actuator in such a manner as to again
request minimum (e.g. zero) light intensity. If the actuator has
arrived at the minimum light level setting before the internal
timer times-out, the selected dimmer will be "locked" to the
adjusted actuator, i.e. the microprocessor will re-program the
look-up table so as to assign the manipulated actuator to the
selected dimmer. If the internal timer times-out before the
actuator arrives at the minimum light level setting, the program
returns to the dimmer-selection step, and the associated lamps on
the selected dimmer begin to flash ON/OFF again.
By virtue of the above apparatus, it will be appreciated that a
user can re-configure an entire lighting system, i.e., re-assign
any or all of the actuators to different dimmers, without ever
having any knowledge of the symbology used in initially programming
the system. Similarly, dimmers can be added to existing zones, or
assigned to previously unassigned actuators without knowledge of
the actuator "numbers."
Referring to FIG. 5, there is shown a functional block diagram of
each of the dimmers discussed above. The general purpose of each
dimmer is to provide a phase control output to its associated
lighting load LL to control the RMS voltage across the load and,
hence, its luminous intensity. As discussed below, each dimmer is
adapted to operate on a wide range of input voltages from 80 VAC to
277 VAC, 50 or 60 Hz. A circuit breaker CB functions in a
conventional manner to provide AC overcurrent protection. It also
functions as a means for removing power to a dimmer, each dimmer
having its own breaker. A relay R serves to break power to the load
and operates under the control of a microprocessor MP. The switched
power of the relay serves to provide power directly to a
controllably conductive device, preferably a triac T, and it can
also be used to provide a switched hot output necessary for dimming
fluorescent loads. The microprocessor controls the turn on sequence
of the relay and triac so that the relay contacts are closed with
no current through them. The triac responds to a control signal on
its gate lead to selectively conduct a portion of the AC line
voltage during each half cycle thereof, whereby the RMS voltage
across the load can be varied. The triac's ON time is controlled by
the microprocessor and is based on the digital values received on
the communications link MUX' from the control assigned thereto. As
discussed below, a plurality of address switches provide each
dimmer on the communications link a unique address so that each
dimmer can identify zone intensity information intended for it.
Each dimming circuit also includes a full wave bridge circuit FWB
which rectifies the AC line voltage to provide the DC voltage
needed to operate the microprocessor and relay coil. A power supply
PS uses the rectified AC line voltage to provide 30 volts DC to
operate the relay. The power supply also derives a regulated 5 VDC
supply to power the microprocessor. A zero-cross detector ZC senses
when the line voltage waveform crosses zero and provides an input
to the microprocessor for determining the line frequency and phase.
A voltage compensation circuit, discuused below, operates to
maintain a constant light intensity even when the AC line voltage
fluctuates from its nominal value. As also discussed below, the
microprocessor is programmed to respond to various inputs,
including a triac fault detector FD, to indicate the operating
status of the system and various key components. Such status is
indicated by a causing status indicator SI, preferably a single LED
or other light source, to flash according to a predetermined
sequence. A large choke C (e.g. up to 2 or 3 millihenry) is
connected in series with the triac output and serves to suppress
RFI and reduce lamp buzzing in incandescent lamps.
In the lighting control system described above, it is noted that
the dimming control panel circuit CP controls the respective
outputs of the dimmers (Dimmer1-Dimmer N in FIG. 1). Preferably,
communication between the control panel circuit and dimmer circuits
is carried out on a two-wire serial data link MUX' to which the
dimmers are connected in a daisy-chain fashion. So that each dimmer
responds only to intensity information intended for it, each dimmer
is commonly assigned a different binary or digital address. In
prior art systems, such addressing has been achieved either by an
array of bi-stable "DIP" switches, each having an actuator that can
be moved between two stable positions, or a rotary, multipositional
selector switch which, based on the position of a rotatable
selector element, determines the dimmer address. In the event a
dimmer requires replacement, it will be appreciated that the new
unit must have the same address as the defective unit. This
requires some attention to detail by the servicing personnel in
that an unobserved accidental movement of one of the switch
actuators on the DIP switch array, or a rotation of the selector
element of the defective unit prior to setting the address of the
new unit can be problematic in setting the address of the new unit.
Ideally, the replacement dimmer should be self-addressing so as to
eliminate human involvement in the addressing process.
According to a second aspect of this invention, there is provided a
digital dimmer that automatically addresses itself as it is mounted
on a support plate. The features which enable it to be
self-addressing are better shown in FIG. 6. As shown, each dimmer
module, designated as reference character 50, comprises a housing
52, e.g., a circuit board, which is mountable in a predetermined
location L' (shown in phantom lines in FIG. 6) on a support plate
SP. The dimmer circuit board supports the various electronic
components (discussed below with reference to FIG. 12) required to
vary the intensity of a lighting load in response to receiving a
suitable lighting control signal. As noted above, such components
include a triac T which is used to selectively interrupt power to
the load to dim its output. According to a preferred embodiment,
each dimmer module 50 has a unique binary address code determined
by an array of normally open address switches 56-60, located at the
periphery of the circuit board, and means associated with the
support plate for selectively changing the conductive state of one
or more of the switches as the dimmer module is mounted in a
predetermined location L' on the support plate. Preferably, each of
the switches is of the type which includes a movable plunger P
which, depending on its extended or retracted position, determines
the conductive (open or closed) state of its associated switch.
Normally, the plunger of such switches is spring-biased towards its
extended position, in which case the switch is normally open.
Preferred address switches are the "Detector Switches," made by
Matsushita Electronics Components, Co. When address switches of
this type are used, the switch-closing means on the support plate
may take the form of an array A of holes H having lands L
therebetween and on opposite sides thereof. When the dimmer module
is properly positioned on the support plate, the holes act to allow
some of the plungers to remain in their normally extended position,
thereby allowing their respective switches to remain open, while
the lands act to selectively depress the remaining switch plungers,
thereby closing their respective switches. Thus, it will be
appreciated that the dimmer's address is determined by the
hole/land pattern opposite the position in which it is mounted. By
using different hole/land patterns, each dimmer module can receive
a unique binary address code. Preferably, a plurality of dimming
modules are mounted on the same support plate and, opposite each
position on the plate which is to receive a dimmer module, a
different hole/land pattern is formed.
In the self-addressing scheme described above, each of the address
switches includes a pair of contacts which are shown in the
electrical schematic of FIG. 12. One contact of each pair is
connected to a voltage source. In response to switch closure, a
signal appears at the switch output. The respective outputs of the
address switches serve as High/Low inputs to a microprocessor
forming part of the dimmer. Prior to accepting intensity
information from the dimmer control panel over the multiplex link,
the binary address produced by the address switches must match the
address transmitted on the serial data link.
In the preferred embodiment shown in FIG. 6, there are a total of
five address switches 56-60 which define a five-bit binary address
code. Obviously, the number of switches is determined by the
maximum number of dimmers allowed on the communications link. As
noted, the dimmers have predefined mounting locations on the
support plate, each of such locations being determined by a pair of
spaced guides 62 which engage the lateral edges of a module's
circuit board. Each guide is provided with opposing grooves so that
adjacent circuit boards can share the same guide. Each guide is
provided with a pair of mounting clips 63 which are designed to
snap into engagment with apertures 64 formed in the support plate.
When the mounting clips are positioned within the apertures 64, a
pair of feet 65 on each guide engage the support plate surface at
locations 66. When so positioned, guides 62 serve to postion the
circuit board upright (perpendicular) with respect to the support
plate surface.
While the above embodiment uses an array of electromechanical
switches and support plate holes and lands to provide the
self-addressing feature, other self-addressing schemes come to
mind. For example, magnetic address switches can be used which
cooperate with a magnetic/non-magnetic pattern on the support
plate. Alternatively, photoelectric switches can be used which
cooperate with a reflective/non-reflective pattern on the support
plate.
Referring now to FIGS. 7 and 8, another aspect of this invention
relates to the dimmer support plate and the arrangement of the
heat-generating dimmer components thereon to achieve a relatively
high packing density of dimmer modules. As noted earlier, each
dimmer includes, in addition to a triac or the like, a relatively
large choke or coil for suppressing RFI. When the dimmer is
operating, both of these components generate so much heat that it
is common to provide some sort of heat sink for conducting heat
away from the other circuit elements to avoid damage or, at least,
prolong their useful life. Often, a number of dimmers comprising a
dimming panel are supported on a common, heat-conducting, support
plate with the heat-generating components of each dimmer being
thermally coupled to the plate. Usually, the support plate is a
casting or extrusion having a plurality of fins or ribs on the
opposite side thereof for radiating the heat conducted thereto into
the surrounding air. Ideally, the RFI choke, being the larger
producer of thermal energy, should be remotely spaced from its
associated dimmer components, but since conventional dimmers are
packaged with the choke included, the choke is usually positioned
relatively close to its associated circuit components.
As an alternative to using relatively costly castings or extrusion
of finned surfaces and the like, and to mounting the
choke-containing dimmers side-by-side on a flat, heat-conducting
support plate, it is preferred that the support plate take the form
of a corrugated metal structure, and that all of the RFI chokes be
mounted, side-by-side, in a portion of the plate remote from the
other dimming circuit components. Since the chokes are merely
copper windings that are relatively insensitive to the high
temperature levels that result from grouping the chokes together,
there is no disadvantage, other than the necessary rewiring that
results, in locating the chokes remote from the dimmers. The
advantage of this arrangement is that the heat generated by the
triac can be easily dissipated in the support plate, and the
semiconductor circuit elements of the dimming module can operate at
a low operating temperature, thereby prolonging their life.
Referring FIG. 7, the support plate SP is depicted as a corrugated
structure having alternating lands 80 and channels 82. Preferably,
the support plate is made of aluminum, about 3 mm in thickness, and
the corrugated structure is provided by appropriately bending the
plate. Such a corrugated structure has the effect of enlarging the
surface area over which heat can be dissipated without enlarging
the overall dimensions of the plate. In accordance with a preferred
embodiment, the lands and channels are rectilinear, parallel and
approximately equal in width, preferably about 40 mm wide, and the
depth of the channels is approximately 30 mm. In the dimming panel
shown in FIG. 7, sixteen dimmers D1-D16 and their associated chokes
C1-C16 are mounted on a common corrugated support. Since the chokes
are relatively insensitive to heat, they are mounted as close
together as practical, on both the lands 80 and in the channels 82,
as better shown in FIG. 8. Since heat rises, it is preferred that
the chokes occupy the upper portion of the support plate with the
dimmers mounted below. Preferably, the dimmers are mounted on only
the land (or the base of the channel) portions of the support plate
to provide more thermal isolation from the heat produced by the
respective triacs of adjacent dimmers. Since the central region of
the support plate will attain a higher temperature than the
peripheral portions, it is also preferred that the dimmer modules
be arranged in the pattern shown, with gradually fewer modules in
the direction of the plate center.
An advantageous technical effect of the corrugated configuration of
the support plate is that a chimney effect is created between
adjacent lands and channels in which the radiated heat is quickly
dispersed in a direction parallel to the longitudinal axes of the
lands and channels. This chimney effect is maximized, of course, by
arranging the support plate such that the channels extend
vertically, whereby the heat-generated is free to rise uninhibited.
Further, the corrugated configuration of the support plate serves
to substantially increase the thermal separation of the dimming
circuits. The combination of the corrugated support plate and the
remotely located RFI chokes provides a low-cost, yet highly
efficient, scheme for reducing the ambient temperature in the
vicinity of the heat-sensitive dimmer components, thereby
increasing their expected lifetime. Also, as many as twenty-four 16
ampere dimming circuits and their associated 2 millihenry chokes
can be housed on a common support plate measuring only about 70 cm.
by about 85 cm. in overall dimension.
Another aspect of this invention enables a system user or installer
to have temporary lighting even in the absence of a dimmer control
signal. In the past, a loss or absence of the control signal would
necessitate the use of jumper cables or the like to by-pass the
dimmer and thereby apply full power to the lighting load. According
to this aspect of the invention, the user need only cycle a circuit
breaker (i.e., turn the input power circuit breaker off and on) in
order to provide temporary lighting of a preset intensity, e.g.,
full ON. Referring to FIG. 9, the flow chart illustrates preferred
steps carried out by the dimmer's microprocessor in implementing
this feature.
Upon powering up the system, the dimmer's microprocessor MP
determines whether power has been applied to its associated dimmer
module. If it has, the microprocessor then determines whether any
valid data has been received from the dimmer control panel circuit
CP since power-up. This is determined by monitoring the input data
on the communication link MUX'. If no data has been received since
the initial power-up, the microprocessor operates the triac to
provide full power (or any predefined preset level) to the lighting
load. If valid data has been received, the microprocessor continues
to monitor the communications link for valid data and operates the
lighting load at an intensity determined by such data. When the
microprocessor determines that valid data is no longer being
received, it determines whether valid data has been received since
the last power up. If so, it freezes the lamp intensity at the
power level requested prior to loss of data. If not, the lighting
load is operated at full intensity, or some other preset value. If
power has been removed from the dimmer module after the light
intensity has been frozen at some level, such as by switching off
the circuit breaker, the program returns to the beginning of the
program and, as soon as power is restored, such as by switching on
the circuit breaker, the microprocessor will operate the lamps at
full intensity, or some preset level. If power to the dimmer has
not been interrupted after the light intensity has been frozen at
some level, the microprocessor keeps checking for valid data on the
multiplex link and, until valid data appears, the light level
remains frozen. Should valid data eventually appear, the lights are
operated at the intensity requested.
From the foregoing, it will be appreciated that the dimmer can be
by-passed in the absence of a control signal by simply turning the
circuit breaker CB in FIG. 5 off and on. Power to the load will
then be controlled strictly by the circuit breaker as if the dimmer
was a short circuit. Normal operation will be immediately restored
upon detection of a proper multiplex control signal or valid
data.
According to another aspect of this invention, the dimmer module of
FIG. 5 preferably includes a unique voltage compensation circuit VC
which operates to provide a constant lamp output even when the A.C.
line voltage fluctuates from a wide variety of nominal values. The
voltage compensation circuitry (shown in detail in the electrical
schematic of FIG. 12) allows a capacitor to charge up to a
reference level during each half-cycle of the A.C. waveform. The
microprocessor allows the capacitor to start charging as the A.C.
line voltage crosses zero, as determined by the zero-crossing
detector ZC, and measures the time it takes to charge to the
reference voltage. This charging time is a function of the
amplitude of the A.C. line voltage; the higher the line voltage,
the faster the charging time. The time measured during each half
cycle is compared to a long term (e.g. 15 second) average. An error
signal is derived from the comparison, and such signal is used to
adjust the triac firing angle in such a manner as to keep the
output voltage from changing. The result is that the effects of
fast-changing and short lived changes in line voltage, sags and
surges, are minimized.
While the voltage compensation scheme described above can be used
with any conventional line voltage, it will be appreciated that the
nominal charging time will vary substantially with the nominal line
voltage. That is, if a single charging capacitor is used for all
nominal line voltages, it may be relatively easy, based on its
value, to detect variations in charging times at low line voltages,
e.g. between 80 and 160 volts, and relatively difficult to detect
such variations at high line voltages, e.g., between 160 and 277
volts . Thus, to facilitate the charging time measurement for a
wide range of line voltages, it is preferred that two different
capacitor values be used, a relatively low value for relatively low
line voltages, and a relatively high value for relatively high line
voltages. Preferably an additional capacitor is switched into a
parallel circuit with the normal charging capacitor when the
microprocessor detects that the nominal line voltage exceeds a
certain level (e.g., 160 volts).
The steps carried out by the microprocessor in compensating for
line voltage fluctuations are shown in FIG. 10. Upon initially
applying power to the dimmer, the microprocessor delays about 15
seconds before providing voltage compensation. This time period
allows the microprocessor to determine a "long term" average for
the charging time of the capacitor(s). Referring to the electrical
schematic of FIG. 12, capacitor C8 is the charging capacitor when
the line voltage is between 80 and 160 volts, and capacitors C8 and
C9 are the charging capacitors when the nominal line voltage
exceeds 160 volts. A zero-crossing detector comprising diodes D4,
D5, and resistors R6 and R8, provides the reference point from
which the charging time is measured. The zero-crossing detector is
connected to the output of the diode bridge DB1 which provides full
wave rectification of the A.C line voltage. The output of the
zero-crossing detector provides an input to the microprocessor.
Until a zero crossing of the line voltage occurs, the
microprocessor shorts the capacitor. In response to a zero
crossing, the microprocessor allows the capacitor C8 to charge.
When a predetermined threshold or reference level is reached, as
determined by the values of zener diode D9 and resistor R26, the
microprocessor stores the charging time of the capacitor and
discharges the capacitor until the next zero crossing. If the
measured charging time is shorter than a certain minimum value, the
microprocessor then determines whether the charging capacitor
selected is adapted for the low nominal voltages. If so, the line
voltage is too high for proper operation, and a reset is forced. If
the measured charging time is not shorter than the minimum allowed
value, then the microprocessor determines whether the charging time
is longer than a certain allowed value. If so, the microprocessor
determines whether the capacitance adapted for use with high line
voltages has been selected. If so, the line voltage is too high for
proper operation, and a reset is forced. If not, the lower
capacitance is selected, and the program returns to the 15 second
delay step. If the measured charging time is neither shorter than
an allowed minimum value, nor longer than an allowed maximum value,
the microprocessor determines the error between the measured
charging time and the long term average. The long term average is
then updated by subtracting or adding a fraction of the new
charging time, and the firing angle of the triac is adjusted by an
amount based on the error, load type and present firing angle.
In multizone lighting systems of the type described, it is often
difficult to identify which dimmer module may have failed in the
event of a system malfunction. Usually, test equipment and a
skilled technician are required. Also, it is necessary to determine
whether the malfunction is indeed due to a dimmer failure, or
simply a misprogrammed control scheme. Conventional systems use an
indicator lamp to indicate a very basic status level, e.g., power
on/off.
According to another aspect of this invention, each dimmer is
equipped with means for monitoring several status states of the
dimmer and for providing a visible indication thereof. Preferably,
the status indicator takes the form of a single light source which
can be selectively energized in different ways to indicate
different status conditions, as diagnosed by the dimmer module's
microprocessor MP. Preferably, the diagnostic light source is a
conventional LED. In response to different inputs indicative, for
example, of the status of the communications link, power to the
dimmer module, status of the dimmer's power-switching component
(triac), control unit status, etc., the microprocessor causes the
LED to "blink" according to a readily recognizable pattern, for
example, once every second, once every other second, once every
third second, several times per second, etc. The status indicated
by the blinking LED is recorded in documentation provided the
system user.
Referring to FIG. 11, the flow chart illustrates the various
preferred steps carried out by the microprocessor MP in diagnosing
the status of its associated dimmer module. First, it is determined
whether the dimmer module has power applied to it. This is achieved
by monitoring the line source voltage applied to the dimmer. If no
power is applied to the dimmer, the LED will be off. If power is
applied, the microprocessor determines whether the dimmer module's
triac is either shorted or open circuited. This is done by the
circuitry described below with reference to FIG. 12. If the triac
has failed, the microprocessor causes the status indicator (an LED)
to flash several times per second. If the triac is operating
properly, the microprocessor determines whether the dimmer is
receiving serial data from a control unit over the multiplex link.
If no data is received, the LED is blinked on and off slowly, e.g.,
on for two seconds, and off for four seconds. If data is received,
the microprocessor determines whether the dimmer relay is open. If
not, thus indicating that the dimmer is operating but the control
is telling dimmer to be off, the LED is blinked on for, say 1/4
second, and off for 3/4 second. If the dimmer relay is closed, the
LED is blinked on for, say 3/4 second, and off for 1/4 second. This
process is continuously repeated to provide a constant update on
the dimmer/system status.
In FIG. 12, a preferred circuit for the dimmer described above is
shown in detail. The various circuit elements of each of the
functional blocks shown in FIG. 5 are shown in dashed lines of each
block. The AC power circuit includes the circuit breaker S1, relay
S2, triac Q5 and RFI choke L1. As mentioned earlier, the circuit
breaker provides overcurrent protection and the ability to
disconnect AC power to the dimming module. The relay S2 is used to
disconnect power to the load being controlled by the dimming module
and is controlled by the microprocessor U1. The conduction of triac
Q5 is also controlled by the microprocessor in such a manner as to
limit conduction to a portion of each AC line cycle; such portion
is determined by the zone intensity information provided by one of
the wallmounted controls on the multiplex link. Pin 38 of U1 turns
on the optically-coupled triac U2 through R14. The current through
R16, U2, R17, D7 and D6 triggers the gate of Q5 and forces it to
conduct. Once Q5 is conducting, U2 remains on by the current path
formed by R18 and R19. This is done to drive high impedance loads
with current levels below the holding current of Q5. Capacitor C7
is connected across the gate to cathode of Q5 to improve its
resistance to false triggering due to noise. The rate of rise of
the load current is limited by the choke L1 to reduce the audible
noise (buzzing) in the lamp caused by the abrupt change in current
when the Q5 is turned on. The choke also serves, as indicated
above, to limit the amount of RFI noise generated by the switching
action of Q5. The microprocessor U1 and the relay S1 require DC
supply voltages much lower in amplitude than the AC line amplitude.
To provide this voltage, the AC line is rectified through the diode
bridge DB1 and dropped across a high voltage field-effect
transistor FET Q4. Q4 is allowed to turn on whenever Q3 is off. Q3
will be off when the rectified line voltage is less than the sum of
the voltages across the zener diode D2 and the drop across the
resistor R1 and R1'. The voltage generated across R1 and R1' needed
to turn on Q3 is determined by the value of R15. Resistors R1, R1'
and R15 form a voltage divider network to bias the base of Q3. The
values are selected to limit the peak voltage on Q4 to within its
safe operating area. Resistors R2 and R2' provide a means to turn
on Q4 when Q3 is off. Resistor R3 serves to slow the charging of
the gate capacitor to minimize the RFI noise generated on the AC
line when Q4 switches. D11 limits the peak voltage on the gate of
Q4. With the values selected, capacitor C1 is allowed to charge to
a maximum value of 32 VDC. If Q4 is on long enough to try to charge
C1 higher, D1 will be biased on, thereby forcing Q3 on and Q4
off.
Once C1 is charged to its maximum value the voltage is used to
drive the relay and the microprocessor. The current needed to drive
the relay is greater than that required by the microprocessor and
the control circuit.
To reduce the peak current draw through Q4 and minimize power
dissipation when the relay is energized, the current through the
relay coil is used to generate the 5 VDC supply needed for the
microprocessor. When the relay is off, the 32 VDC supply is dropped
across Q1. The zener D13 allows C2 to charge to 5 V. Q1 is biased
on through R29, and the base voltage is clamped by diodes D15 and
D18. When the relay coil is energized, Q8 is turned on by U1, R11,
Q2 and R4. The current through the relay coil charges C2 to a value
limited by diodes D14 and D13. While D14 is conducting, Q1 is
forced off. Hence, C2 can only be charged by the current through
the relay coil when the relay is energized.
To control the timing of the gate of Q5, i.e., the triac's firing
angle, the AC line zero cross must be known by the microprocessor.
This information is provided by the zero-cross detector comprising
resistor R6, R6' and the protection diodes D4 and D5. Since the
microprocessor is referenced inside the bridge DB1, alternate half
cycles of the line voltage force the voltage on pins 41 and 39 of
the microprocessor between 5 V and common. The edges of the
transitions define the AC line zero crossing. The microprocessor
also requires dimming control information to compute the delay from
the zero crossing to turn on the triac during each half cycle. As
noted above, this information is received by the dimmer through the
serial data link MUX'. A voltage is applied across R7 and pins 1
and 2 of U3 to produce an output through R12, Q7 and R24 into pin
32 of U1. An optically-coupled device is used to provide isolation
between the dimmer circuitry referenced to Class I voltage and the
Class II circuitry which sends control information to each
dimmer.
The input data received received on the data link is in the form of
a string of bits which, in addition to indicating a desired zone
intensity, also indicates the load type e.g., incandescent,
fluorescent, etc., and maximum and minimum light settings (high and
low end trim settings, respectively). The microprocessor uses this
information to compute a delay time to turn on the gate of Q5 in
each AC half cycle after each AC zero crossing.
Since many dimmer modules may exist on a single serial data link,
each dimmer module must have a unique address. The address switches
S1, S2, S4, S8, and S16 along with RN1 and RN2 provide inputs to
the microprocessor defining a unique combination of up to 32
different addresses.
Light-emitting diode D8 and resistor R20 provide a diagnostic
status indicator. The microprocessor causes the LED to "blink" in
such a manner as to indicate normal operation or failure modes. One
such failure mode is triac Q5 being either open or short circuited.
R25, R25', D16 and D17 provide an input into to the microprocessor
which signifies a fault condtion by the presence or absence of
voltage at certain points in each half cycle. Another defined
failure is the absence of data being received on the serial data
link.
The micrprocessor also receives an input from the voltage
compensation network which it uses to correct the firing angle of
the triac during to compensate for variations in the AC line
voltage. This correction forces the output voltage of the dimmer to
remain relatively constant during these variations. The rectified
AC line voltage is taken from the full-wave bridge DB1 through D12.
Resistors R5, R5', and capacitor C8 form an integrator to "smooth"
the 60 Hz ripple of the rectified line voltage. This filtered
voltage varies proportionally with the amplitude of the AC line and
is used to charge capacitors C9 and C6 through resistor R9. C9 may
be switched in and out through R8 and pin 15 of the microprocessor
to change the time constant to accomodate different ranges of AC
line voltages. C6 is used for 80-160 VAC and C6 plus C9 is used for
160-277 VAC. The capacitors are discharged by R10 and pin 13 of the
microprocessor. The microprocessor allows the capacitors to start
charging at the AC zero crossing. When the capacitor's voltage
reach a threshold level determined by D9, and R26, transistor Q6
turns on and pulls pin 2 of the microprocessor low through R22. The
microprocessor measures the charging time of the capacitors and
uses it to determine the amount of correction needed. The
microprocessor contains the ROM required to store the program that
receives the various inputs and determines the turn-on point of
triac Q5 in each AC line cycle. U4 and R13 form an oscillator
needed to run the microprocessor.
The invention has been described with particular reference to
preferred embodiments. It will be appreciated the certain
variations and modifications can be made without departing from the
spirit of the invention. Such variations and modifications are
intended fall within the protected scope of the invention, as
defined by the appended claims.
* * * * *